A runner reacts near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts.

"We're working very closely with our local and federal law enforcement counterparts,'' said Jan Caldwell, a spokeswoman for the San Diego County Sheriff's Department. "These appear to be tragic, isolated events in Boston.

We have no indication there is any (local) threat ... . If that changes, we will immediately let the community know.''

Likewise, the San Diego Police Department's personnel were being extra vigilant due to the bombings, SDPD public information officer Gary Hassen said.

"We're aware of what happened in Boston ... and there is a heightened awareness (on the part of) our officers,'' Hassen said.

He declined to disclose whether the department had increased or shifted patrols, or instituted any other out-of-the-ordinary measures.

"We do not discuss security (publicly),'' he said.

Administrators at Lindbergh Field made no immediate changes, since the Transportation Security Administration had not directed them to do so, according to airport spokeswoman Rebecca Bloomfield.

"We'll take our cues from TSA,'' she said.

Twenty members of the San Diego Track Club took part in the marathon along with scores of other people from San Diego County, which has "a very large running community,'' said Kate Garcia, president of the organization.

"As far as I know, everyone (from this area) is OK,'' she said.

Among the track club's contingent, 18 had completed the race when the explosives detonated, and the other two had not gotten close enough to the finish line to have been in any danger, Garcia said.